Lock-up device for fluid coupling

ABSTRACT

It is an object of the present invention to provide a lock-up device for a fluid coupling that can reliably suppress vibration caused by coil springs. It is to provide a lock-up device for a fluid coupling that can reliably suppress vibration caused by coil springs. This lock-up device ( 7 ) is equipped with an input rotation member ( 30 ) and ( 31 ), an output rotation member ( 35 ), plural first elastic members ( 32 ), and a float member ( 42 ). The first elastic members ( 32 ) are compressed in a rotational direction by the relative rotation of the input rotation member and the output rotation member. The float member ( 42 ) is placed in such a way as to be rotatable relative to the input rotation member ( 30 ) and ( 31 ) in order to cause two of the first elastic members ( 32 ) to act in series in a circumferential direction.

CROSS-REFERENCE TO THE RELATED APPLICATIONS

This U.S. national phase application claims priority to Japanese PatentApplication Nos. 2010-252579 and 2010/275613 filed on Nov. 11, 2010 andDec. 10, 2010 respectively. The entire disclosure of Japanese PatentApplication Nos. 2010-252579 and 2010/275613 is hereby incorporatedherein by reference

BACKGROUND

1. Technical Field

The present invention relates to a lock-up device and particularly to alock-up device for a fluid coupling for transmitting torque andabsorbing and damping torsional vibration.

2. Background Art

There are many cases where a lock-up device for directly transmittingtorque from a front cover to a turbine is disposed in torque converters.The lock-up device is equipped with a piston, a drive plate, pluralouter peripheral side torsion springs, a driven plate, plural innerperipheral side torsion springs, and a middle member (see patentcitation 1). The piston is coupleable to the front cover. The driveplate is coupled to the piston. The torque is input from the drive plateto the plural outer peripheral side torsion springs. The driven plate iscoupled to the turbine. The plural inner peripheral side torsion springsare arranged on the inner peripheral side of the outer peripheral sidetorsion springs and transmit the torque to the driven plate. The middlemember is rotatable relative to the drive plate and the driven plate andtransmits the torque from the outer peripheral side torsion springs tothe inner peripheral side torsion springs.

CITATION LIST Patent Literature

-   Patent Citation 1: JP-A No. 2001-82577

SUMMARY Technical Problem

In lock-up devices, widening the torsion angle of the damper iseffective in order to efficiently absorb and damp torque fluctuationsinput from the engine. Therefore, in the lock-up device described inpatent citation 1, the torsion angle of the damper is designed wide byarranging the torsion springs on the outer peripheral portion and theinner peripheral portion and using the middle member to couple togetherthe outer peripheral side torsion springs and the inner peripheral sidetorsion springs in series.

In recent years, there has been a demand to lower fuel consumption byfurther improving characteristics. For example, consider a case wherethe technology of Japanese Patent No. 3,717,772 is used in addition tothe well-known technology described above. In this case, not only canthe outer peripheral side torsion springs and the inner peripheral sidetorsion springs be coupled together in series by the middle member, buttwo of the outer peripheral side torsion springs can also be coupledtogether in series via a float member. Because of this, the torsionangle of the damper can be designed wider and the demand described abovecan be satisfied.

However, in a case where the torsion angle of the damper has beenwidened in this way, there is the concern that a normal mode resultingfrom adding the float member will occur. For example, in a case wherethe float member has been added, the potential for the normal mode tobecome manifest in the high speed range becomes higher, and when thenormal mode appears in the normal speed range of the engine, there isthe concern that unpleasant vibrations and vibration sounds will end upoccurring.

The present invention has been made in view of this problem, and it isan advantage of the present invention to keep the vibration level of alock-up device in an allowable range.

Solution to Problem

A lock-up device for a fluid coupling pertaining to claim 1 is a lock-updevice for a fluid coupling for transmitting torque and absorbing anddamping torsional vibration. The lock-up device for a fluid couplingincludes an input rotation member, an output rotation member, pluralfirst elastic members, and a float member. The plural first elasticmembers are compressed in a rotational direction by the relativerotation of the input rotation member and the output rotation member.The plural first elastic members are arranged adjacently in thecircumferential direction in a predetermined position in a radialdirection. The float member is placed in such a way as to be rotatablerelative to the input rotation member in order to cause at least two ofthe first elastic members among the plural first elastic members to actin series in a circumferential direction. In this lock-up device, in theat least two first elastic members that act in series in thecircumferential direction because of the float member, the free lengthof either one of the first elastic members is made shorter than the freelength of the other of the first elastic members, whereby the rigidityof the either one of the first elastic members is set greater than therigidity of the other of the first elastic members.

In this lock-up device, when the torque from the engine is input to theinput rotation member, the torque is transmitted to the output rotationmember via the plural first elastic members. Further, the at least twofirst elastic members among the plural first elastic members are coupledtogether in series in the circumferential direction by the float member.Here, the free length of either one of the at least two first elasticmembers coupled together in series in the circumferential direction isshorter than the free length of the other of the first elastic members,so the rigidity of the first elastic member with the short free lengthbecomes greater than the rigidity of the other first elastic member.

Here, an outline of the vibration level of the lock-up device will bedescribed as basic information for describing the effects of the presentlock-up device. For example, considering the vibration curve(speed-vibration level curve; reference curve; see the dashed line inFIG. 5) of the lock-up device in a case where the float member is notpresent, in this reference curve, the normal mode (primary mode) of thelock-up device appears below the lock-up speed Na for example.Additionally, in this reference curve, the higher the speed becomes themore the vibration level falls. On the other hand, the vibration curveof the lock-up device in a case where the float member is presentbecomes one where the vibration component of the float member issuperimposed on this reference curve (see the solid line in FIG. 5). Forthis reason, in the vibration curve in a case where the float member ispresent, as the speed at which vibration of the float member occursbecomes higher, the speed at which the vibration component of the floatmember becomes prominent—that is, the speed at which the float memberresonates—also becomes higher. Considering this fact in combination withthe fact that, in the reference curve described above, the higher thespeed becomes the more the vibration level falls, when the speed atwhich the float member resonates becomes high, the resonance level ofthe float member (component of reference curve+resonance component offloat member) falls.

In a case where the resonance speed of the float member in the presentlock-up device has been found on the basis of this consideration, theresonance speed of the float member is affected by the at least twofirst elastic members arranged in series in the circumferentialdirection because of the float member. For example, in a case where thefirst elastic members arranged in series in the circumferentialdirection because of the float member have been set to different lengths(a case where the first elastic members have been set to differentrigidities), the resonance speed of the float member becomes highercompared to a case where the first elastic members have been set to thesame lengths (a case where the first elastic members have been set tothe same rigidities). In this way, in the present lock-up device, bysetting the first elastic members arranged in series in thecircumferential direction because of the float member to differentlengths, the resonance speed of the float member can be set to a higherspeed than the resonance speed of the well-known float member. Becauseof this, in the present lock-up device, the resonance level of the floatmember can be lowered and the vibration level of the lock-up device canbe kept in the allowable range.

A lock-up device for a fluid coupling pertaining to claim 2 is thedevice of claim 1 and further includes plural second elastic members anda middle member. The plural second elastic members are arranged oneither one of an inner peripheral side and an outer peripheral side ofthe plural first elastic members and transmit the torque to the outputrotation member. The middle member is placed in such a way as to berotatable relative to the input rotation member in order to transmit thetorque from the first elastic members to the second elastic members.

Here, the lock-up device further includes the plural second elasticmembers and the middle member, and the torque from the engine istransmitted from the first elastic members to the second elastic membersvia the middle member. In this way, even if the torsion angle of thedamper has been widened, in the present lock-up device, by setting thefirst elastic members arranged in series in the circumferentialdirection because of the float member to different lengths, theresonance speed of the float member can be set to a higher speed thanthe resonance speed of the float member. Because of this, in the presentlock-up device the resonance level of the float member can be lowered,and the vibration level of the lock-up device can be kept in theallowable range.

A lock-up device for a fluid coupling pertaining to claim 3 is thedevice according to claim 1 or 2, wherein in the at least two firstelastic members that act in series in the circumferential directionbecause of the float member, the first elastic member with the shortfree length is placed on the side to which the torque is input by theinput rotation member.

Here, the first elastic member with the short free length is placed onthe input side. In a case where the resonance speed of the float memberhas been calculated as described above, the resonance speed of the floatmember can be made higher by making the rigidity of the first elasticmember with the short free length (the first elastic member on the inputside) higher than the rigidity of the other elastic member. Because ofthis, in the present lock-up device, the resonance level of the floatmember can be efficiently lowered, and the vibration level of thelock-up device can be kept in the allowable range.

A lock-up device for a fluid coupling pertaining to claim 4 is thedevice according to claim 1 or 2, wherein in the at least two firstelastic members that act in series in the circumferential directionbecause of the float member, the first elastic member with the long freelength is placed on the side to which the torque is input by the inputrotation member.

Here, the first elastic member with the long free length is placed onthe input side. In a case where the resonance speed of the float memberhas been calculated as described above, the resonance speed of the floatmember can be made higher by making the first elastic member with theshort free length (the rigidity of the first elastic member on the inputside) higher than the rigidity of the other elastic member. In otherwords, the resonance speed of the float member can be made lower bymaking the first elastic member with the long free length (the rigidityof the first elastic member on the input side) lower than the rigidityof the other first elastic member.

Here, generally there is tendency for the resonance speed of the floatmember to approach the lock-up speed in the normal speed range thegreater the number of cylinders in the engine there are. In this case,there is the concern that the lock-up device will end up being stronglyaffected by the resonance of the float member at the lock-up speed. Insuch a case as this, by placing the first elastic member with the longfree length on the input side, the resonance speed of the float membercan be set to a lower speed range than the lock-up speed. Because ofthis, the effect of the resonance of the float member in the normalspeed range can be removed. That is, in the present lock-up device, thevibration level of the lock-up device can be kept in the allowablerange.

A lock-up device for a fluid coupling pertaining to claim 5 is thedevice according to any of claims 1 to 4, wherein the free lengths ofthe at least two first elastic members are set in such a way that thesum total of the free lengths of the at least two elastic members thatact in series in the circumferential direction because of the floatmember becomes fixed. For example, in the at least two first elasticmembers that act in series in the circumferential direction because ofthe float member, the free lengths of the first elastic members are setin such a way that the sum total of the free length of either one of thefirst elastic members and the free length of the other elastic memberbecomes a predetermined length. In this case, even if the free length ofeither one of the first elastic members has been made shorter, the freelength of the other first elastic member becomes longer in accordancetherewith, so it is ensured that the total rigidity of the at least twofirst elastic members that act in series in the circumferentialdirection because of the float member is constant. That is, theresonance speed of the float member can be set to a higher speed thanthe resonance speed of the well-known float member while maintaining thenormal mode (primary mode) of the lock-up device below the lock-upspeed, for example. Because of this, resonance problems with the lock-updevice can be reliably prevented in the normal range.

A lock-up device for a fluid coupling pertaining to claim 6 is a lock-updevice for a fluid coupling for transmitting torque and absorbing anddamping torsional vibration. The lock-up device for a fluid couplingincludes an input rotation member, an output rotation member, pluralsets of first elastic members, and a float member. The plural sets offirst elastic members are compressed in a rotational direction by therelative rotation of the input rotation member and the output rotationmember. The plural sets of the first elastic members are arrangedadjacently in a circumferential direction in a predetermined position ina radial direction. Further, the plural sets of the first elasticmembers are rotatable relative to the float member. One set of the firstelastic members is configured by plural spring members. The pluralspring members are arranged in series continuously in thecircumferential direction. The float member restricts the movement ofthe spring members (first elastic members) in the radial direction.

In this lock-up device, when the torque from the engine is input to theinput rotation member, the torque is transmitted to the output rotationmember via the plural sets of the first elastic members. Here, theplural sets of the first elastic members are arranged adjacently in thecircumferential direction in a predetermined position in the radialdirection. Here, the plural sets of the first elastic members arerotatable relative to the float member, and the movement of the pluralsets of the first elastic members in the radial direction is restrictedby the float member. In this state, when the torque is input to each setof the first elastic members, the plural spring members configuring eachset of the first elastic members act in series in the circumferentialdirection.

Here, an outline regarding the vibration level of the well-known lock-updevice will be described as basic information for describing the effectsof the present lock-up device. Considering the vibration curve(speed-vibration level curve; reference curve; see the solid line inFIG. 5) of the lock-up device in a case where the float member ispresent, in this reference curve, the normal mode (primary mode) of thelock-up device appears below the lock-up speed Na for example.Additionally, the normal mode of the float member appears in the rangeof a speed greater than the lock-up speed Na. Hereinafter, the speed Nfat which the normal mode of the float member appears will be called thespeed at which the vibration component of the float member becomesprominent—that is, the resonance speed of the float member.

In this well-known lock-up device, the normal mode of the float memberappears because the float member is incorporated in the vibrationsystem. Specifically, in the well-known lock-up device, the normal modeof the float member appears because the float member is caused to engagewith two spring members whereby the two spring members are caused to actin series in the circumferential direction. With respect thereto, in thepresent lock-up device, the float member restricts the movement of thefirst elastic members in the radial direction but is not caused toengage with the first elastic members. Specifically, the plural springmembers are arranged in series continuously in the circumferentialdirection without involving the float member. Further, the plural springmembers are rotatable relative to the float member. Because of this, inthe present lock-up device, the vibration component of the float membercan be removed from the vibration system. That is, in the presentlock-up device, the resonance resulting from the float member can beremoved from the vibration system. Because of this, in the presentlock-up device, the vibration level can be kept in the allowable range.

A lock-up device for a fluid coupling pertaining to claim 7 is thedevice according to claim 6, wherein both end portions of each of theplural spring members and the float member are rotatable relative toeach other.

Here, both end portions of each of the plural spring members and thefloat member are rotatable relative to each other, so the plural springmembers act in series continuously in the circumferential directionwithout involving the float member. For this reason, in the presentlock-up device, the vibration component of the float member—that is, theresonance resulting from the float member—can be removed from thevibration system. Because of this, in the present lock-up device, thevibration level can be kept in the allowable range.

A lock-up device for a fluid coupling pertaining to claim 8 is thedevice according to claim 6 or 7, wherein the torque is transmitted inthe order of the input rotation member, the plural sets of the firstelastic members, and the output rotation member.

Here, the torque is transmitted in the order of the input rotationmember, the plural sets of the first elastic members, and the outputrotation member. That is, the torque is transmitted via the plural setsof the first elastic members from the input rotation member to theoutput rotation member without involving the float member. For thisreason, in the present lock-up device, the vibration component of thefloat member—that is, the resonance resulting from the float member—canbe removed from the vibration system. Because of this, in the presentlock-up device, the vibration level can be kept in the allowable range.

A lock-up device for a fluid coupling pertaining to claim 9 is thedevice according to any of claim 6 or 8, wherein the plural springmembers are arranged in series continuously in the circumferentialdirection via seat members.

Here, the plural spring members are arranged in series continuously inthe circumferential direction via the seat members, so the plural springmembers can be caused to act in series continuously in thecircumferential direction. Because of this, torque fluctuations can bereliably transmitted to the plural spring members. Further, torquefluctuations can be efficiently absorbed and damped in the springmembers.

A lock-up device for a fluid coupling pertaining to claim 10 is thelock-up device for a fluid coupling according to any of claims 6 to 9,wherein the plural spring members are arranged in series directly andcontinuously in the circumferential direction.

Here, the plural spring members are arranged in series directly andcontinuously in the circumferential direction. For example, the pluralspring members are arranged in series continuously in thecircumferential direction as a result of adjacent end portions of theplural spring members being brought into contact with each other. Morespecifically, the plural spring members are arranged in seriescontinuously in the circumferential direction as a result of adjacentend turn portions of the plural spring members being brought intocontact with each other. In this way, in the present lock-up device,special members such as spring seats become unnecessary, so the numberof parts can be reduced and the plural spring members can be easilyassembled.

A lock-up device for a fluid coupling pertaining to claim 11 is thelock-up device for a fluid coupling according to any of claims 6 to 10,wherein the spring members are configured from either one of linear coilsprings and arc-shaped coil springs. Here, either one of linear coilsprings and arc-shaped coil springs is used as the spring members, sotorsion characteristics with various variations can be easily designed.

A lock-up device for a fluid coupling pertaining to claim 12 is thelock-up device for a fluid coupling according to any of claims 6 to 11and further includes plural second elastic members and a middle member.The plural second elastic members are arranged on either one of an innerperipheral side and an outer peripheral side of the plural sets of thefirst elastic members and transmit the torque to the output rotationmember. The middle member is placed in such a way as to be rotatablerelative to the input rotation member in order to transmit the torquefrom the first elastic members to the second elastic members.

Here, the lock-up device further includes the plural second elasticmembers and the middle member, and the torque from the engine istransmitted from the first elastic members to the second elastic membersvia the middle member. In this way, even if the torsion angle of thedamper has been widened, in the present lock-up device, the vibrationcomponent of the float member—that is, the resonance resulting from thefloat member—can be removed from the vibration system, so the vibrationlevel can be kept in the allowable range.

Advantageous Effects of Invention

According to the present invention as described above, the vibrationlevel of a lock-up device can be kept in an allowable range.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional partial view of a torque converter equippedwith a lock-up device according to a first embodiment of the presentinvention;

FIG. 2 is a front partial view of the lock-up device;

FIG. 3 is a vibration model of a well-known lock-up device;

FIG. 4 is a conceptual diagram showing the torsion characteristic of thewell-known lock-up device;

FIG. 5 is a conceptual diagram showing the vibration level of thewell-known lock-up device;

FIG. 6 is a vibration model of the lock-up device;

FIG. 7 is a conceptual diagram showing the torsion characteristic of thelock-up device;

FIG. 8 is a conceptual diagram showing the vibration level of thelock-up device;

FIG. 9 is a cross-sectional partial view of a torque converter accordingto another embodiment different from the first embodiment;

FIG. 10 is a cross-sectional partial view of a torque converter equippedwith a lock-up device according to a second embodiment of the presentinvention;

FIG. 11 is a front partial view of the lock-up device;

FIG. 12 is a vibration model of a well-known lock-up device;

FIG. 13 is a conceptual diagram showing the torsion characteristic ofthe well-known lock-up device;

FIG. 14 is a conceptual diagram showing the vibration level of thewell-known lock-up device;

FIG. 15 is a vibration model of the lock-up device;

FIG. 16 is a conceptual diagram showing the vibration level of thelock-up device;

FIG. 17 is a diagram showing a spring seat of a lock-up device accordingto another embodiment different from the second embodiment (1); and

FIG. 18 is a diagram showing a spring seat of a lock-up device accordingto another embodiment different from the second embodiment (2).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Embodiment

FIG. 1 is a cross-sectional partial view of a torque converter 1 inwhich a lock-up device serving as an embodiment of the present inventionis employed. An engine (not shown in the drawings) is placed on the leftside of FIG. 1, and a transmission (not shown in the drawings) is placedon the right side of the drawing. FIG. 2 is a front partial view of thelock-up device. O-O shown in FIG. 1 is an axis of rotation of the torqueconverter and the lock-up device.

Overall Configuration of Torque Converter

The torque converter 1 is a device for transmitting torque from acrankshaft (not shown in the drawings) on the engine side to an inputshaft of the transmission and is configured from a front cover 2 that isfixed to a member on the input side, a torque converter body 6 thatincludes three types of vaned wheels (an impeller 3, a turbine 4, and astator 5), and a lock-up device 7.

The front cover 2 is a disc-shaped member, and an outer peripheralcylindrical portion 10 that projects toward the axial directiontransmission side is formed on the outer peripheral portion of the frontcover 2. The impeller 3 is configured from an impeller shell 12 that isfixed by welding to the outer peripheral cylindrical portion 10 of thefront cover 2, plural impeller blades 13 that are fixed to the innerside of the impeller shell 12, and a cylindrical impeller hub 14 that isdisposed on the inner peripheral side of the impeller shell 12. Theturbine 4 is placed in opposition to the impeller 3 inside a fluidchamber. The turbine 4 is configured from a turbine shell 15, pluralturbine blades 16 that are fixed to the turbine shell 15, and a turbinehub 17 that is fixed to the inner peripheral side of the turbine shell15. The turbine hub 17 has a flange 17 a that extends toward the outerperipheral side, and the inner peripheral portion of the turbine shell15 is fixed to the flange 17 a by plural rivets 18. Further, the inputshaft of the unillustrated transmission is spline-engaged with the innerperipheral portion of the turbine shell 17.

The stator 5 is placed between the inner peripheral portions of theimpeller 3 and the turbine 4 and is a mechanism for redirectinghydraulic oil returning from the turbine 4 to the impeller 3. The stator5 is mainly configured from a disc-shaped stator carrier 20 and pluralstator blades 21 that are disposed on the outer peripheral surface ofthe stator carrier 20. The stator carrier 20 is supported on anunillustrated fixing shaft via a one-way clutch 22. A thrust washer 25is disposed between the front cover 2 and the turbine hub 17 in theaxial direction, and thrust bearings 26 and 27 are disposed between theturbine hub 17 and the stator carrier 20 and between the stator carrier20 and the impeller shell 12, respectively.

Lock-up Device

The lock-up device 7 is placed in an annular space between the frontcover 2 and the turbine 4. The lock-up device 7 mainly has a piston 30,a drive plate 31, plural outer peripheral side and inner peripheral sidetorsion springs 32 and 33, a middle member 34 that couples together theouter peripheral side torsion springs 32 and the inner peripheral sidetorsion springs 33, and a driven plate 35.

Here, the piston 30 and the drive plate 31 correspond to an inputrotation member, and the driven plate 35 corresponds to an outputrotation member. Further, the outer peripheral side torsion springs 32correspond to first elastic members, and the inner peripheral sidetorsion springs 33 correspond to second elastic members.

Piston

The piston 30 is a disc-shaped plate member and is placed in such a wayas to divide the space between the front cover 2 and the turbine 4 intwo in the axial direction. The outer peripheral portion of the piston30 is a flat friction coupling portion 30 a, and a friction facing 37 isdisposed on the axial direction engine side of the friction couplingportion 30 a. A flat friction surface is formed on the front cover 2 inopposition to the friction facing 37. Further, an inner peripheralcylindrical portion 30 b that extends toward the axial directiontransmission side is disposed on the inner peripheral edge of the piston30. The inner peripheral surface of the inner peripheral cylindricalportion 30 b is supported in such a way as to be movable in the axialdirection and the rotational direction with respect to the outerperipheral surface of the turbine hub 17. In a state in which the distalend of the inner peripheral cylindrical portion 30 b is in contact withpart of the turbine hub 17, the movement of the piston 30 toward theaxial direction transmission side is restricted. A seal ring 38 isdisposed between the inner peripheral cylindrical portion 30 b and theouter peripheral surface of the turbine hub 17.

In this way, a space A is formed between the front cover 2 and thepiston 30. The outer peripheral portion of the space A is blocked in astate in which the friction facing 37 is in contact with the front cover2, and the inner peripheral portion of the space A is in communicationwith an oil passage formed in the input shaft via a groove formed in thethrust washer 25.

Drive Plate

The drive plate 31 is an annular member made of a metal plate and isplaced on the axial direction transmission side of the friction couplingportion 30 a of the piston 30. The inner peripheral portion of the driveplate 31 is fixed to the piston 30 by plural rivets 40. Further, pluralcatch portions 31 a that extend toward the axial direction transmissionside are formed on the outer peripheral portion of the drive plate 31.The plural catch portions 31 a are formed a predetermined interval apartfrom each other in the circumferential direction and support the endfaces of the outer peripheral side torsion springs 32. Moreover, asupport portion 31 b that extends toward the axial directiontransmission side is formed above the portion of the drive plate 31attached to the piston. The inner peripheral sides of the outerperipheral side torsion springs 32 are supported by the support portion31 b.

Outer Peripheral Side Torsion Springs

The plural outer peripheral side torsion springs 32 are arrangedadjacently in the circumferential direction in a predetermined positionin the radial direction. The plural outer peripheral side torsionsprings 32 are configured from plural pairs of the outer peripheral sidetorsion springs 32. Here, there are two outer peripheral side torsionsprings 32 in one set, for a sum total of eight outer peripheral sidetorsion springs 32.

The free lengths of the two outer peripheral side torsion springs 32 ofeach set are set in such a way that the sum total of the free lengths ofthe two outer peripheral side torsion springs 32 of each set becomes apredetermined length. Further, the free lengths of the two outerperipheral side torsion springs 32 of each set are set in such a waythat one free length of either of the two outer peripheral side torsionsprings 32 of each set is shorter than the other free length of eitherof the two outer peripheral side torsion springs 32 of each set. In FIG.2, the outer peripheral side torsion spring 32 with the short freelength is short is denoted by sign 32 a, and the outer peripheral sidetorsion spring 32 with the long free length is denoted by sign 32 b.

Further, because the two outer peripheral side torsion springs 32 ofeach set are set in such a way that the sum total of the free lengths ofthe two outer peripheral side torsion springs 32 of each set becomes apredetermined length, if one free length of either of the two outerperipheral side torsion springs 32 of each set is short, the other freelength of either of the two outer peripheral side torsion springs 32 ofeach set becomes longer in correspondence thereto.

Further, the free lengths of the outer peripheral side torsion springs32 are set in such a way that the ratio of the other free length ofeither of the two outer peripheral side torsion springs 32 of each setwith respect to one free length of either of the two outer peripheralside torsion springs 32 of each set falls in the range of 1.1 to 2.5. Inthis way, by setting the sum total of the free lengths of the two outerperipheral side torsion springs 32 of each set to a predetermined lengthand setting the free lengths of the outer peripheral side torsionsprings 32 in the range of the ratio described above, the outerperipheral side torsion spring 32 b with the long free length can berestricted in such a way that there is no close inter-wire contact at anearly stage.

Here, the sum total of the free lengths of the two outer peripheral sidetorsion springs 32 of each set is set to 140 mm. Further, the freelength of the outer peripheral side torsion spring 32 a with the shortfree length is set to 60 mm, and the free length of the outer peripheralside torsion spring 32 b with the long free length is set to 80 mm.

In the two outer peripheral side torsion springs 32 of each setdescribed above, the outer peripheral side torsion spring 32 a with theshort free length is placed on the input side. Here, in a case wheretorsional vibration has occurred in the lock-up device 7 and the piston30 and the drive plate 31 have rotated in the direction of R1 in FIG. 2,the spring that is pressed in the direction of R1 by the piston 30 andthe drive plate 31 is the outer peripheral side torsion spring 32 a withthe short free length. The direction of R1 corresponds to the mainrotational direction of the engine.

Further, a float member 42 is disposed in the neighborhood of the outerperipheral side torsion springs 32 so that the two outer peripheral sidetorsion springs 32 of each set act in series. The float member 42 is anannular member with a C-shaped cross section and is placed above thesupport portion 31 b of the drive plate 31. The float member 42 isplaced in such a way as to be rotatable relative to the drive plate 31.The outer peripheral portion of the float member 42 supports the outerperipheral portions of the outer peripheral side torsion springs 32.That is, the outer peripheral side torsion springs 32 are restrictedfrom popping out toward the outer peripheral side by the float member42. Axial direction transmission side distal end portions 42 a of thefloat member 42 are bent toward the inner peripheral side and the engineside, and bent portions 42 a of the distal end portions are insertedbetween the outer peripheral side torsion springs 32 of each set. Thatis, both circumferential direction end faces of the bent portions 42 aare in contact with the end faces of the corresponding torsion springs32.

As described above, in the plural outer peripheral side torsion springs32, both circumferential direction ends of the outer peripheral sidetorsion springs 32 of each set are supported by the catch portions 31 aof the drive plate 31, and the bent portions 42 a of the float member 42are inserted between the outer peripheral side torsion springs 32 ofeach set. Further, the outer peripheral portions of the outer peripheralside torsion springs 32 are supported by the outer peripheral portion ofthe float member 42.

Middle Member

The middle member 34 is an annular, disc-shaped plate member placedbetween the piston 30 and the turbine shell 15. The middle member 34 isconfigured from a first plate 44 and a second plate 45. The first plate44 and the second plate 45 are placed an interval apart from each otherin the axial direction. The first plate 44 is placed on the axialdirection transmission side, and the second plate 45 is placed on theaxial direction engine side. The outer peripheral portions of the firstplate 44 and the second plate 45 are coupled together by plural stopperpins 46 in such a way that the first plate 44 and the second plate 45are non-rotatable relative to each other and are immovable in the axialdirection. Window portions 44 a and 45 a that penetrate the first plate44 and the second plate 45 in the axial direction are formed in thefirst plate 44 and the second plate 45, respectively. As is apparentfrom FIG. 1 and FIG. 2, the window portions 44 a and 45 a are formedextending in the circumferential direction, and cut-and-raised portionsthat have been cut and raised in the axial direction are formed on theinner peripheral portions and the outer peripheral portions of thewindow portions 44 a and 45 a.

Further, plural catch portions 44 b that extend as far as the outerperipheral side torsion springs 32 are formed on the outer peripheralend of the first plate 44. The plural catch portions 44 b are formed bybending the distal ends of the first plate 44 toward the axial directionengine side. The plural catch portions 44 b are arranged a predeterminedinterval apart from each other in the circumferential direction, and theouter peripheral side torsion springs 32 of each set that act in seriesare placed between two of the catch portions 44 b.

Inner Peripheral Side Torsion Springs

The plural inner peripheral side torsion springs 33 are placed insidethe window portions 44 a and 45 a of both plates 44 and 45 of the middlemember 34. Additionally, both circumferential direction ends and bothradial direction sides of each of the inner peripheral side torsionsprings 33 are supported by the window portions 44 a and 45 a. Moreover,the inner peripheral side torsion springs 33 are restricted from poppingout in the axial direction by the cut-and-raised portions of the windowportions 44 and 45.

Driven Plate

The driven plate 35 is an annular, disc-shaped member, and its innerperipheral portion is fixed to the flange 17 a of the turbine hub 17 bythe rivets 18 together with the turbine shell 15. The driven plate 35 isplaced between the first plate 44 and the second plate 45 in such a wayas to be rotatable relative to both plates 44 and 45. Additionally,window holes 35 a are formed in the outer peripheral portion of thedriven plate 35 in correspondence to the window portions 44 a and 45 aof the first and second plates 44 and 45. The window holes 35 a areholes that penetrate the driven plate 35 in the axial direction, and theinner peripheral side torsion springs 33 are placed in the window holes35 a. Further, as indicated by a dashed line in FIG. 2, plural cutouts35 b that are long in the circumferential direction are formed in theouter peripheral portion of the driven plate 35. Additionally, thestopper pins 46 penetrate the cutouts 35 b in the axial direction.Consequently, the driven plate 35 and both plates 44 and 45 configuringthe middle member 34 are rotatable relative to each other in the angularranges in which the cutouts 35 b are formed.

Operation

Next, the operation will be described. The torque from the crankshaft onthe engine side is input to the front cover 2. Because of this, theimpeller 3 rotates and hydraulic oil flows from the impeller 3 to theturbine 4. Because of the flow of the hydraulic oil, the turbine 4rotates and the torque of the turbine 4 is output to the unillustratedinput shaft.

The speed ratio of the torque converter 1 increases, and when the inputshaft reaches a prescribed rotational speed, the hydraulic oil in thespace A is drained through the oil passage inside the input shaft. As aresult, the piston 30 is moved toward the front cover 2 side. As aresult, the friction facing 37 of the piston 30 is pressed against thefriction surface of the front cover 2 and the torque of the front cover2 is output to the lock-up device 7.

In the lock-up device 7, the torque is transmitted in the order of thepiston 30, the drive plate 31, the outer peripheral side torsion springs32 (32 a and 32 b), the middle member 34, the inner peripheral sidetorsion springs 33, and the driven plate 35 and is output to the turbinehub 17.

The lock-up device 7 transmits the torque and absorbs and damps torquefluctuations input from the front cover 2. Specifically, when torsionalvibration occurs in the lock-up device 7, the outer peripheral sidetorsion springs 32 and the inner peripheral side torsion springs 33 arecompressed in series between the drive plate 31 and the driven plate 35.Moreover, regarding the outer peripheral side torsion springs 32 also,the outer peripheral side torsion springs 32 of each set are compressedin series. For this reason, the torsion angle can be widened. Moreover,because the outer peripheral side torsion springs 32 that can take along circumferential direction distance are caused to act in series, awider torsion angle can be ensured. This means that the torsioncharacteristic can be lowered in rigidity, so that the vibrationabsorption and damping performance can be further improved.

The outer peripheral side torsion springs 32 and the inner peripheralside torsion springs 33 act until the stopper pins 46 come into contactwith the end faces of the cutouts 35 b formed in the driven plate 35,and only the outer peripheral side torsion springs 32 act (the innerperipheral side torsion springs 33 do not act) after the stopper pins 46have come into contact with the end faces of the cutouts 35 b.Consequently, the lock-up device 7 has a two-stage torsioncharacteristic.

Here, the outer peripheral side torsion springs 32 try to move towardthe outer peripheral side because of centrifugal force. For this reason,a member that restricts the movement of the outer peripheral sidetorsion springs 32 toward the outer peripheral side becomes necessary.In this embodiment, the outer peripheral portions of the outerperipheral side torsion springs 32 are supported by the float member 42,whereby the movement of the outer peripheral side torsion springs 32toward the outer peripheral side is restricted. At this time, the floatmember 42 moves together with the outer peripheral side torsion springs32, so sliding resistance can be reduced compared to a case where theouter peripheral portions of the outer peripheral side torsion springsare supported by the drive plate like in a well-known device.

Further, in this embodiment, the outer peripheral side torsion springs32 and the inner peripheral side torsion springs 33 are coupled togetherby the middle member 34, so the overall hysteresis torque becomes thecoupling of the inner peripheral side and outer peripheral sidehysteresis torques. That is, in the present embodiment, the hysteresistorque of the outer peripheral side torsion springs 32 is smaller andthe hysteresis torque of the inner peripheral side torsion springs 33 isnot different, so the overall hysteresis torque also becomes smaller.For this reason, the vibration absorption and damping performance can beimproved and lower fuel consumption can be realized because of theexpansion of the lock-up range.

Characteristics and Effects of Lock-up Device

Here, first, before giving a description of the present lock-up device7, a description of a case where the free lengths and the rigidities ofthe two outer peripheral side torsion springs 32 of each set are set tobe identical will be given. This corresponds to a well-known lock-updevice, and other configurations excluding the outer peripheral sidetorsion springs 32 are the same as those of the present lock-up device.The torsion characteristic in this case is also a two-stage torsioncharacteristic such as described above. A model diagram showing thetwo-stage torsion characteristic is shown in FIG. 3. Sign E shown inFIG. 3 represents the engine, and sign T represents the transmission.Further, sign Dr, sign F, sign M, and sign Dv represent the drive plate,the float member, the middle member, and the driven plate, respectively.Moreover, a conceptual diagram of the torsion characteristic in thiscase and a conceptual diagram of the vibration level (fluctuation level)of the lock-up device are shown in FIG. 4 and FIG. 5.

In this case, the outer peripheral side torsion springs 32 and the innerperipheral side torsion springs 33 operate until the stopper pins 46come into contact with the end faces of the cutouts 35 b formed in thedriven plate 35. For this reason, the overall rigidity Ko1 becomes“Ko1=1/(2/K11+1/K13)” (see FIG. 4). Here, K11 is the rigidity of each ofthe two outer peripheral side torsion springs 32 of each set, and K13 isthe rigidity of the inner peripheral side torsion springs 33.Additionally, only the outer peripheral side torsion springs 32 operateafter the stopper pins 46 have come into contact with the end faces ofthe cutouts 35 b formed in the driven plate 35. For this reason, theoverall rigidity Ko2 becomes “Ko2=K11/2”.

Referring to FIG. 5, in the well-known lock-up device, the normal mode(primary mode) of the lock-up device is set below the lock-up speed Na.Additionally, as the speed increases, the vibration level (amount offluctuation) falls. However, when the speed approaches a predeterminedspeed, the vibration level again rises. This speed is the resonancespeed Nf of the float member. In the well-known lock-up device, there isthe concern that the vibration level at this resonance speed Nf willbecome higher than the allowable level.

The vibration level in FIG. 5 corresponds to fluctuations in therotation of the transmission, and the speed in FIG. 5 corresponds to theengine speed. Further, No in FIG. 5 corresponds to the natural frequencyat which the normal mode of the lock-up device becomes prominent, and Nfcorresponds to the resonance speed at which the mode of the float memberbecomes prominent. Further, So represents the upper limit of theallowable value of the vibration level. Moreover, the unit of thevertical axis and the horizontal axis in FIG. 5 is rpm. The descriptionthat has been given here is also applied to FIG. 8 described later.

In the case of the present lock-up device 7, the free lengths—that is,the rigidities—of the two outer peripheral side torsion springs 32 ofeach set are different. A model diagram showing the two-stage torsioncharacteristic in this case is shown in FIG. 6. The signs shown in FIG.6 have the same meanings as those of the signs described in FIG. 3.Further, in FIGS. 6, 11 and 12 are shown, and these are the secondarymoments of inertia of each member. Moreover, a conceptual diagram of thetorsion characteristic in this case and a conceptual diagram of thevibration level (fluctuation level) of the lock-up device 7 are shown inFIG. 7 and FIG. 8.

Next, a description of the present lock-up device 7 will be given. Inthe present lock-up device 7, the outer peripheral side torsion springs32 and the inner peripheral side torsion springs 33 operate until thestopper pins 46 come into contact with the end faces of the cutouts 35 bformed in the driven plate 35. For this reason, the overall rigidity KK1becomes “KK1=1/(1/K1+1/K2+1/K3)” (see FIG. 7). Here, K1 and K2 are therigidities of the outer peripheral side torsion springs 32, and K3 isthe rigidity of the inner peripheral side torsion springs 33.Additionally, only the outer peripheral side torsion springs 32 operateafter the stopper pins 46 have come into contact with the end faces ofthe cutouts 35 b formed in the driven plate 35. For this reason, theoverall rigidity KK2 becomes “KK2=(1/K1+1/K2)”.

Here, in the present lock-up device 7, one free length of either of thetwo outer peripheral side torsion springs 32 of each set is made shorterthan the other free length of either of the two outer peripheral sidetorsion springs 32 of each set, whereby one rigidity K1 of either of thetwo outer peripheral side torsion springs 32 of each set is set in sucha way as to be larger than the other rigidity K2 of either of the twoouter peripheral side torsion springs 32. That is, the relationship of“K1>K2” is established. More specifically, in the present lock-up device7, the relationship of “K1>K11>K2” is established. Because of this, inthe present lock-up device 7, the overall rigidity KK1 becomes “K11≈Ko1”and the overall rigidity KK2 becomes “KK2≈Ko2”.

In this way, the overall rigidity KK1 of the present lock-up device 7 issubstantially the same as the overall rigidity Ko1 in the case where thetwo outer peripheral side torsion springs 32 of each set are the same,so in the present lock-up device 7 also, as shown in FIG. 8, the normalmode (primary mode) of the lock-up device 7 can be maintained below thelock-up speed Na. Additionally, as the speed increases and approachesthe resonance speed Nf′ of the float member 42, the vibration levelrises. However, in the present lock-up device 7, as described above, theouter peripheral side torsion spring 32 a with the short free length isplaced on the input side, whereby the resonance speed Nf′ of the floatmember 42 becomes higher than the resonance speed Nf shown in FIG. 5(Nf′>Nf). Because of this, the vibration level at this resonance speedNf′ becomes lower than the vibration level shown in FIG. 5, and as shownin FIG. 8, the vibration level at this resonance speed Nf′ can be keptbelow the allowable level.

The resonance speed (the resonance speed Nf′ shown in FIG. 8) at whichthe vibration of the float member 42 becomes prominent in the presentlock-up device 7 is evaluated by“Nf′=½π×{½×[(K1+K2)/I1+(K2+K3)/I2]−[¼×[(K1+K2)/I1−(K2+K3)/I2]²+K22/(I1·I2)]^(1/2)}^(1/2)”.

Looking at this evaluation formula, it will be understood that therigidity K1 of the outer peripheral side torsion spring 32 on the inputside (that is, the engine side) (the rigidity of the outer peripheralside torsion spring 32 a with the short free length) has a greatereffect on the resonance speed Nf′ than the rigidity K2 of the outerperipheral side torsion spring 32 b with the long free length. Inconsideration of this, in the present lock-up device 7, the outerperipheral side torsion spring 32 a with the short free length is placedon the input side.

Settings and Effects of Torsion Springs

In a general lock-up device, the sum total of the free lengths of thetwo outer peripheral side torsion springs 32 of each set is set to apredetermined length. For example, a length obtained by subtracting thecircumferential direction length of the bent portion 42 a of the floatmember 42 from the circumferential direction length between two catchportions 31 a of the drive plate 31 adjacent to each other in thecircumferential direction corresponds to the predetermined length.Setting the sum total of the lengths of the two outer peripheral sidetorsion springs 32 of each set to the predetermined length in this waymeans that there is a limit with respect to adjusting each of the outerperipheral side torsion springs 32.

Further, generally, if the wire diameter of the outer peripheral sidetorsion springs used in the lock-up device is made too narrow, the outerperipheral side torsion springs end up becoming fatigued because ofrepeated stress, and there is the concern that their performance willend up significantly falling. For this reason, it is necessary to setthe wire diameter of the outer peripheral side torsion springs equal toor greater than a predetermined minimum value.

Here, in the well-known lock-up device, if the resonance speed Nf (seeFIG. 5) of the float member 42 is set to a higher speed in order tolower the vibration level of the float member 42, it is necessary toraise the rigidity of either one of the two outer peripheral sidetorsion springs of each set. This can be realized by increasing the wirediameter of either one of the two outer peripheral side torsion springsof each set.

However, because it is necessary to ensure a certain extent of thicknessfor the wire diameter of the outer peripheral side torsion springs asdescribed above, here, if the wire diameter of either one of the twoouter peripheral side torsion springs of each set is increased, theentire rigidities Ko1 and Ko2 end up becoming higher. When this happens,the normal mode of the lock-up device shifts to the high speed side andthe vibration level at the lock-up speed Na rises. When this happens,there is the concern that vibration and vibration noise resulting fromthe normal mode of the lock-up device will end up occurring in thenormal range.

Further, because it is necessary to place the two outer peripheral sidetorsion springs of each set in the limited spaces between two catchportions 31 a of the drive plate 31 adjacent to each other in thecircumferential direction, in a case where the wire diameter of eitherone of the two outer peripheral side torsion springs of each set hasbeen increased, close inter-wire contact ends up occurring at an earlystage and there is the concern that the performance of the lock-updevice will end up becoming unable to be sufficiently exhibited.

In the present lock-up device 7, one wire diameter (a first wirediameter) of either one of the two outer peripheral side torsion springs32 of each set is set to a predetermined value. Further, the other wirediameter (a second wire diameter) of either one of the two outerperipheral side torsion springs 32 of each set is set to a predeterminedvalue. The predetermined values indicated here are values equal to orgreater than the above-described predetermined minimum value. Further,it is not invariably necessary for the first wire diameter and thesecond wire diameter to be the same size.

In the two outer peripheral side torsion springs 32 of each set, thefree length of one of the outer peripheral side torsion springs 32 isset shorter than the free length of the other of the outer peripheralside torsion springs 32 without changing the wire diameters (the firstwire diameter and the second wire diameter) of the outer peripheral sidetorsion springs 32. Here, the free length of the one outer peripheralside torsion spring 32 is set short in the range of the above-describedlimit, and in accordance with this the free length of the other outerperipheral side torsion spring 32 is set long. By setting the two outerperipheral side torsion springs 32 of each set in this way, as describedin “[Characteristics and Effects of Lock-up Device]”, the rigidity ofone of the outer peripheral side torsion springs 32 is set larger thanthe rigidity of the other of the outer peripheral side torsion springs32 without greatly changing the overall rigidity KK1.

Because of this, in the present lock-up device 7, as shown in FIG. 8,the vibration level at the resonance speed Nf′ of the float member 42can be kept below the allowable level in a state in which the vibrationlevel at the lock-up speed Na is maintained. That is, the performance ofthe lock-up device 7 can be sufficiently exhibited.

Other Embodiments Different from First Embodiment

(a) The present invention is not limited to the above embodiment and iscapable of various modifications and revisions without departing fromthe scope of the present invention. For example, in the aboveembodiment, the elastic members were configured by coil springs, butother elastic members formed out of resin or the like can also be used.Further, the numbers and lengths of the coil springs configuring theouter peripheral side and inner peripheral side torsion springs are notlimited to the above embodiment. Moreover, the float member is forplacing at least two torsion springs (elastic members) in series on thesame circumference, and the shape of the float member is not limited tothe above embodiment.

(b) In the above embodiment, an example of a case where the outerperipheral side torsion spring 32 a with the short free length is placedon the input side was described. This assumes a case where the number ofcylinders in the engine is small, such as a case where an engine withless than eight cylinders, for example, is used. Assuming a case wherethe number of cylinders in the engine is large, such as a case where anengine with eight cylinders or more, for example, is used, there is theconcern that the resonance speed Nf of the float member will appear inthe neighborhood of the lock-up speed Na in the normal speed range. Forexample, there is the concern that the value of |Nf−Na| in FIG. 5 willend up becoming smaller and end up being strongly affected by theresonance of the float member 42 at the lock-up speed Na. In a case suchas this, the resonance speed Nf of the float member 42 is set to a lowerspeed range than the lock-up speed Na by placing the first elasticmember 32 b with the long free length on the input side. Because ofthis, the effect of the resonance of the float member in the normalspeed range (>Na) can be eliminated. That is, the vibration level of thelock-up device 7 can be kept in the allowable range.

(c) In the above embodiment, an example of a case where the torsionsprings 32 a and 32 b supported by the float member 42 are arranged onthe outer peripheral side was described, but the arrangement of thetorsion springs 32 a and 32 b supported by the float member 42 is notlimited to the above embodiment and can be any arrangement. For example,the radial direction arrangement of the outer peripheral side torsionsprings 32 a and 32 b and the inner peripheral side torsion springs 33in FIG. 1 and FIG. 2 can also be reversed. An example of this case isshown in FIG. 9. In FIG. 9, torsion springs 133 are arranged on theouter peripheral side and torsion springs 132 a and 132 b are arrangedon the inner peripheral side. The inner peripheral side torsion springs132 a and 132 b are arranged in series via a float member 142.

Here, the inner peripheral side torsion springs 132 a and 132 b arearranged in such a way as to act in series using the float member142—for example, two float members 142. The two float members 142 areformed in annular shapes. The two float members 142 are arranged inopposition to each other above the inner peripheral side torsion springs132 a and 132 b. Outer peripheral portions 142 a of the two floatmembers 142 support the outer peripheral portions of the innerperipheral side torsion springs 132 a and 132 b. Further, engagementportions 142 b that engage between the two inner peripheral side torsionsprings 132 a and 132 b are formed on the inner peripheral sides of theouter peripheral portions 142 a of the float members 142. The engagementportions 142 b are sections that project inward from the outerperipheral portions 142 a and are disposed a predetermined intervalapart from each other in the circumferential direction. Bothcircumferential direction end faces of the engagement portions 142 b arein contact with the end faces of the corresponding torsion springs 132 aand 132 b.

In this case, a driven plate 135 engages with the torsion springs 133and is attached to a turbine shell 115 on the outer peripheral side ofthe turbine shell 115. When this happens, the torque is transmitted inthe order of a piston 130, a drive plate 131, the torsion springs 132(132 a and 132 b), a middle member 134, the torsion springs 133, and thedriven plate 135 and is output to the turbine hub 17. Even when giventhis configuration, the same effects as those of the above embodimentcan be obtained.

Second Embodiment

FIG. 10 is a cross-sectional partial view of a torque converter in whicha lock-up device serving as an embodiment of the present invention isemployed. An engine (not shown in the drawings) is placed on the leftside of FIG. 10, and a transmission (not shown in the drawings) isplaced on the right side of the drawing. FIG. 11 is a front partial viewof the lock-up device. O-O shown in FIG. 10 is an axis of rotation ofthe torque converter and the lock-up device.

Overall Configuration of Torque Converter

The torque converter 1 is a device for transmitting torque from acrankshaft (not shown in the drawings) on the engine side to an inputshaft of the transmission and is configured from a front cover 2 that isfixed to a member on the input side, a torque converter body 6 thatincludes three types of vaned wheels (an impeller 3, a turbine 4, and astator 5), and a lock-up device 7.

The front cover 2 is a disc-shaped member, and an outer peripheralcylindrical portion 10 that projects toward the axial directiontransmission side is formed on the outer peripheral portion of the frontcover 2. The impeller 3 is configured from an impeller shell 12 that isfixed by welding to the outer peripheral cylindrical portion 10 of thefront cover 2, plural impeller blades 13 that are fixed to the innerside of the impeller shell 12, and a cylindrical impeller hub 14 that isdisposed on the inner peripheral side of the impeller shell 12. Theturbine 4 is placed in opposition to the impeller 3 inside a fluidchamber. The turbine 4 is configured from a turbine shell 15, pluralturbine blades 16 that are fixed to the turbine shell 15, and a turbinehub 17 that is fixed to the inner peripheral side of the turbine shell15. The turbine hub 17 has a flange 17 a that extends toward the outerperipheral side, and the inner peripheral portion of the turbine shell15 is fixed to the flange 17 a by plural rivets 18. Further, the inputshaft of the unillustrated transmission is spline-engaged with the innerperipheral portion of the turbine shell 17.

The stator 5 is placed between the inner peripheral portions of theimpeller 3 and the turbine 4 and is a mechanism for redirectinghydraulic oil returning from the turbine 4 to the impeller 3. The stator5 is mainly configured from a disc-shaped stator carrier 20 and pluralstator blades 21 that are disposed on the outer peripheral surface ofthe stator carrier 20. The stator carrier 20 is supported on anunillustrated fixing shaft via a one-way clutch 22. A thrust washer 25is disposed between the front cover 2 and the turbine hub 17 in theaxial direction, and thrust bearings 26 and 27 are disposed between theturbine hub 17 and the stator carrier 20 and between the stator carrier20 and the impeller shell 12, respectively.

Lock-up Device

The lock-up device 7 is placed in an annular space between the frontcover 2 and the turbine 4. The lock-up device 7 mainly has a piston 30,a drive plate 31, plural outer peripheral side and inner peripheral sidetorsion springs 32 and 33, a middle member 34 that couples together theouter peripheral side torsion springs 32 and the inner peripheral sidetorsion springs 33, and a driven plate 35.

Here, the piston 30 and the drive plate 31 correspond to an inputrotation member, and the driven plate 35 corresponds to an outputrotation member. Further, the outer peripheral side torsion springs 32correspond to first elastic members, and the inner peripheral sidetorsion springs 33 correspond to second elastic members.

Piston

The piston 30 is a disc-shaped plate member and is placed in such a wayas to divide the space between the front cover 2 and the turbine 4 intwo in the axial direction. The outer peripheral portion of the piston30 is a flat friction coupling portion 30 a, and a friction facing 37 isdisposed on the axial direction engine side of the friction couplingportion 30 a. A flat friction surface is formed on the front cover 2 inopposition to the friction facing 37. Further, an inner peripheralcylindrical portion 30 b that extends toward the axial directiontransmission side is disposed on the inner peripheral edge of the piston30. The inner peripheral surface of the inner peripheral cylindricalportion 30 b is supported in such a way as to be movable in the axialdirection and the rotational direction with respect to the outerperipheral surface of the turbine hub 17. In a state in which the distalend of the inner peripheral cylindrical portion 30 b is in contact withpart of the turbine hub 17, the movement of the piston 30 toward theaxial direction transmission side is restricted. A seal ring 38 isdisposed between the inner peripheral cylindrical portion 30 b and theouter peripheral surface of the turbine hub 17.

In this way, a space A is formed between the front cover 2 and thepiston 30. The outer peripheral portion of the space A is blocked in astate in which the friction facing 37 is in contact with the front cover2, and the inner peripheral portion of the space A is in communicationwith an oil passage formed in the input shaft via a groove formed in thethrust washer 25.

Drive Plate

The drive plate 31 is an annular member made of a metal plate and isplaced on the axial direction transmission side of the friction couplingportion 30 a of the piston 30. The inner peripheral portion of the driveplate 31 is fixed to the piston 30 by plural rivets 40. Further, pluralcatch portions 31 a that extend toward the axial direction transmissionside are formed on the outer peripheral portion of the drive plate 31.The plural catch portions 31 a are formed a predetermined interval apartfrom each other in the circumferential direction and support the endfaces of the outer peripheral side torsion springs 32. Moreover, asupport portion 31 b that extends toward the axial directiontransmission side is formed above the portion of the drive plate 31attached to the piston. The inner peripheral sides of the outerperipheral side torsion springs 32 are supported by the support portion31 b.

Outer Peripheral Side Torsion Springs

As shown in FIG. 11, the plural outer peripheral side torsion springs 32are formed having the same free lengths. Further, the plural outerperipheral side torsion springs 32 are arranged adjacently in thecircumferential direction in a predetermined position in the radialdirection. Plural sets of the outer peripheral side torsion springs 32are configured from pluralities of the outer peripheral side torsionsprings 32. Here, there are two outer peripheral side torsion springs 32in one set, for a sum total of eight outer peripheral side torsionsprings 32. The two outer peripheral side torsion springs 32 of each setof the outer peripheral side torsion springs 32 are arranged adjacentlyin such a way that they act in series mutually.

Further, spring members such as spring seats 52, for example, areattached to both end portions of each of the plural outer peripheralside torsion springs 32. Specifically, each spring seat 52 has a seatportion 52 a and a projecting portion 52 b. The end portions of theouter peripheral side torsion springs 32 contact the seat portions 52 a.The projecting portions 52 b are sections that extend cylindrically fromthe seat portions 52 a, and the projecting portions 52 b arepress-fitted inside the end turns of the outer peripheral side torsionsprings 32.

The two outer peripheral side torsion springs 32 of each set arearranged adjacently in series mutually via the spring seats 52. Further,in a state in which the two outer peripheral side torsion springs 32 ofeach set have been arranged adjacently in series, the spring seats 52 onboth end portions of the two outer peripheral side torsion springs 32arranged in series are in contact with the drive plate 31.

In FIG. 11, the two outer peripheral side torsion springs 32 of one setare denoted by signs 32 a and 32 b. Further, the direction of R1 shownin FIG. 11 corresponds to the main rotational direction of the engine.

A float member 42 is disposed in the neighborhood of the outerperipheral side torsion springs 32, such as on the outer peripheralsides of the outer peripheral side torsion springs 32 for example, inorder to restrict the movement of the outer peripheral side torsionsprings 32 in the radial direction. The float member 42 is an annularmember with a C-shaped cross section and is placed above the supportportion 31 b of the drive plate 31. Specifically, the float member 42 isplaced in such a way as to be rotatable relative to the drive plate 31.The outer peripheral portion of the float member 42 supports the outerperipheral portions of the outer peripheral side torsion springs 32.That is, the outer peripheral side torsion springs 32 are restrictedfrom popping out toward the outer peripheral side by the float member42.

Further, the float member 42 and the outer peripheral side torsionsprings 32 are rotatable relative to each other in the circumferentialdirection. Specifically, the float member 42 and both end portions ofeach of the outer peripheral side torsion springs 32 are rotatablerelative to each other. More specifically, the float member 42 and thespring seats 52 attached to both end portions of each of the outerperipheral side torsion springs 32 are rotatable relative to each other.For this reason, in the present lock-up device 7, the two outerperipheral side torsion springs 32 of each set act in series in thecircumferential direction without involving the float member 42. Becauseof this, the torque is transmitted to the drive plate 31, the outerperipheral side torsion springs 32 (32 a and 32 b), and the middlemember 34 without involving the float member 42.

As described above, both circumferential direction end portions of thetwo outer peripheral side torsion springs 32 of each set—that is, bothend portions of the two outer peripheral side torsion springs 32 a and32 b in a state in which they are adjacent in series in thecircumferential direction—are supported by the catch portions 31 a ofthe drive plate 31 via the spring seats 52. Further, the spring seats 52are in contact with each other at the circumferential direction centralportion of the two outer peripheral side torsion springs 32 of eachset—that is, in the central portion of the two outer peripheral sidetorsion springs 32 a and 32 b in a state in which they are adjacent inseries in the circumferential direction. Because of this, the two outerperipheral side torsion springs 32 of each set act in series mutuallywithout involving the float member and transmit the torque from thedrive plate 31 to the middle member 34.

Middle Member

The middle member 34 is an annular, disc-shaped plate member placedbetween the piston 30 and the turbine shell 15. The middle member 34 isconfigured from a first plate 44 and a second plate 45. The first plate44 and the second plate 45 are placed an interval apart from each otherin the axial direction. The first plate 44 is placed on the axialdirection transmission side, and the second plate 45 is placed on theaxial direction engine side. The outer peripheral portions of the firstplate 44 and the second plate 45 are coupled together by plural stopperpins 46 in such a way that the first plate 44 and the second plate 45are non-rotatable relative to each other and are immovable in the axialdirection. Window portions 44 a and 45 a that penetrate the first plate44 and the second plate 45 in the axial direction are formed in thefirst plate 44 and the second plate 45, respectively. As is apparentfrom FIG. 10 and FIG. 11, the window portions 44 a and 45 a are formedextending in the circumferential direction, and cut-and-raised portionsthat have been cut and raised in the axial direction are formed on theinner peripheral portions and the outer peripheral portions of thewindow portions 44 a and 45 a.

Further, plural catch portions 44 b that extend as far as the outerperipheral side torsion springs 32 are formed on the outer peripheralend of the first plate 44. The plural catch portions 44 b are formed bybending the distal ends of the first plate 44 toward the axial directionengine side. The plural catch portions 44 b are arranged a predeterminedinterval apart from each other in the circumferential direction, and theouter peripheral side torsion springs 32 of each set that act in seriesare placed between two of the catch portions 44 b.

Inner Peripheral Side Torsion Springs

The plural inner peripheral side torsion springs 33 are placed insidethe window portions 44 a and 45 a of both plates 44 and 45 of the middlemember 34. Additionally, both circumferential direction ends and bothradial direction sides of each of the inner peripheral side torsionsprings 33 are supported by the window portions 44 a and 45 a. Moreover,the inner peripheral side torsion springs 33 are restricted from poppingout in the axial direction by the cut-and-raised portions of the windowportions 44 and 45.

Driven Plate

The driven plate 35 is an annular, disc-shaped member, and its innerperipheral portion is fixed to the flange 17 a of the turbine hub 17 bythe rivets 18 together with the turbine shell 15. The driven plate 35 isplaced between the first plate 44 and the second plate 45 in such a wayas to be rotatable relative to both plates 44 and 45. Additionally,window holes 35 a are formed in the outer peripheral portion of thedriven plate 35 in correspondence to the window portions 44 a and 45 aof the first and second plates 44 and 45. The window holes 35 a areholes that penetrate the driven plate 35 in the axial direction, and theinner peripheral side torsion springs 33 are placed in the window holes35 a. Further, as indicated by a dashed line in FIG. 11, plural cutouts35 b that are long in the circumferential direction are formed in theouter peripheral portion of the driven plate 35. Additionally, thestopper pins 46 penetrate the cutouts 35 b in the axial direction.Consequently, the driven plate 35 and both plates 44 and 45 configuringthe middle member 34 are rotatable relative to each other in the angularranges in which the cutouts 35 b are formed.

Operation

Next, the operation will be described. The torque from the crankshaft onthe engine side is input to the front cover 2. Because of this, theimpeller 3 rotates and hydraulic oil flows from the impeller 3 to theturbine 4. Because of the flow of the hydraulic oil, the turbine 4rotates and the torque of the turbine 4 is output to the unillustratedinput shaft.

The speed ratio of the torque converter 1 increases, and when the inputshaft reaches a prescribed rotational speed, the hydraulic oil in thespace A is drained through the oil passage inside the input shaft. As aresult, the piston 30 is moved toward the front cover 2 side. As aresult, the friction facing 37 of the piston 30 is pressed against thefriction surface of the front cover 2 and the torque of the front cover2 is output to the lock-up device 7.

In the lock-up device 7, the torque is transmitted in the order of thepiston 30, the drive plate 31, the outer peripheral side torsion springs32 (32 a and 32 b), the middle member 34, the inner peripheral sidetorsion springs 33, and the driven plate 35 and is output to the turbinehub 17. In particular, in the lock-up device 7, the float member 42 isnot present in the torque transmission path.

The lock-up device 7 transmits the torque and absorbs and damps torquefluctuations input from the front cover 2. Specifically, when torsionalvibration occurs in the lock-up device 7, the outer peripheral sidetorsion springs 32 and the inner peripheral side torsion springs 33 arecompressed in series between the drive plate 31 and the driven plate 35.Moreover, regarding the outer peripheral side torsion springs 32 also,the outer peripheral side torsion springs 32 of each set are compressedin series. For this reason, the torsion angle can be widened. Moreover,because the outer peripheral side torsion springs 32 that can take along circumferential direction distance are caused to act in series, awider torsion angle can be ensured. This means that the torsioncharacteristic can be lowered in rigidity, so that the vibrationabsorption and damping performance can be further improved.

The outer peripheral side torsion springs 32 and the inner peripheralside torsion springs 33 act until the stopper pins 46 come into contactwith the end faces of the cutouts 35 b formed in the driven plate 35,and only the outer peripheral side torsion springs 32 act (the innerperipheral side torsion springs 33 do not act) after the stopper pins 46have come into contact with the end faces of the cutouts 35 b.Consequently, the lock-up device 7 has a two-stage torsioncharacteristic.

Here, the outer peripheral side torsion springs 32 try to move towardthe outer peripheral side because of centrifugal force. For this reason,a member that restricts the movement of the outer peripheral sidetorsion springs 32 toward the outer peripheral side becomes necessary.In this embodiment, the outer peripheral portions of the outerperipheral side torsion springs 32 are supported by the float member 42,whereby the movement of the outer peripheral side torsion springs 32toward the outer peripheral side is restricted.

In the case of using the float member 42, frictional resistance F occursbetween the float member 42 and the outer peripheral side torsionsprings 32. Here, in a case where the inertia torque Tk of the floatmember 42 is equal to or less than the frictional resistance F (Tk≦F; Tk(Nm)=I (kgm²)×ω(rad/m²), the float member 42 rotates together with thelock-up device 7 excluding the float member 42. Here, I is the moment ofinertia and ω is each acceleration. In a case where the inertia torqueTk of the float member 42 has become greater than the frictionalresistance F (Tk>F), the float member 42 and the outer peripheral sidetorsion springs 32 slide and the lock-up device 7 excluding the floatmember 42 becomes rotatable relative to the float member 42.

Here, because the inertia torque Tk of the float member 42 isproportional to the moment of inertia I as described above, it ispreferred that the float member 42 be formed in such a way that themoment of inertia increases. For example, the moment of inertia I of thefloat member 42 can be increased by making the plate thickness of thefloat member 42 thicker. By increasing the moment of inertia I of thefloat member 42 in this way, the lock-up device 7 excluding the floatmember 42 and the float member 42 can be made rotatable relative to eachother at a low speed.

In this way, because the lock-up device 7 excluding the float member 42becomes rotatable relative to the float member 42 in a case where theinertia torque Tk of the float member 42 has become greater than thefrictional resistance F, the vibration component of the float member 42can be removed from the vibration system of the lock-up device 7. Thatis, in the present lock-up device 7, the resonance resulting from thefloat member that had occurred in the well-known lock-up device can beremoved. Because of this, in the present lock-up device 7, as shown inFIG. 16, the vibration level can be kept in the allowable range.

Characteristics and Effects of Lock-up Device

Here, first, before giving a description of the present lock-up device7, a description of a case where the two outer peripheral side torsionsprings 32 of each set act in series via the float member 42 will begiven. This corresponds to a well-known lock-up device. Excluding thepoint that the two outer peripheral side torsion springs 32 of each setact in series via the float member 42, other configurations of thewell-known lock-up device are the same as those of the present lock-updevice 7. The torsion characteristic in this case is also a two-stagetorsion characteristic such as described above. A model diagram showingthe two-stage torsion characteristic is shown in FIG. 12. Sign E shownin FIG. 12 represents the engine, and sign T represents thetransmission. Further, sign Dr, sign F, sign M, and sign Dv representthe drive plate, the float member, the middle member, and the drivenplate, respectively. Moreover, a conceptual diagram of the torsioncharacteristic in this case and a conceptual diagram of the vibrationlevel (fluctuation level) of the lock-up device are shown in FIG. 13 andFIG. 14.

In this case, the outer peripheral side torsion springs 32 and the innerperipheral side torsion springs 33 operate until the stopper pins 46come into contact with the end faces of the cutouts 35 b formed in thedriven plate 35. For this reason, the overall rigidity Ko1 becomes“Ko1=1/(2/K11+1/K12)” (see FIG. 13). Here, K11 is the rigidity of eachof the two outer peripheral side torsion springs 32 of each set, and K12is the rigidity of the inner peripheral side torsion springs 33.Additionally, only the outer peripheral side torsion springs 32 operateafter the stopper pins 46 have come into contact with the end faces ofthe cutouts 35 b formed in the driven plate 35. For this reason, theoverall rigidity Ko2 becomes “Ko2=K11/2”.

Referring to FIG. 14, in the well-known lock-up device, the normal mode(primary mode) of the lock-up device is set below the lock-up speed Na.Additionally, as the speed increases, the vibration level (amount offluctuation) falls. However, when the speed approaches a predeterminedspeed, the vibration level again rises. This speed is the resonancespeed Nf of the float member. In the well-known lock-up device, there isthe concern that the vibration level at this resonance speed Nf willbecome higher than the allowable level.

The vibration level in FIG. 14 corresponds to fluctuations in therotation of the transmission, and the speed in FIG. 14 corresponds tothe engine speed. Further, No in FIG. 14 corresponds to the naturalfrequency at which the normal mode of the lock-up device becomesprominent, and Nf corresponds to the resonance speed at which the modeof the float member becomes prominent. Further, So represents the upperlimit of the allowable value of the vibration level. Moreover, the unitof the vertical axis and the horizontal axis in FIG. 14 is rpm. Thedescription that has been given here is also applied with respect toFIG. 16 described later.

In the case of the present lock-up device 7, the two outer peripheralside torsion springs 32 of each set and the float member 42 arerotatable relative to each other. A model diagram showing the two-stagetorsion characteristic in this case is shown in FIG. 15. The signs shownin FIG. 15 have the same meanings as those of the signs described inFIG. 12. Further, a conceptual diagram of the vibration level(fluctuation level) of the lock-up device 7 in this case is shown inFIG. 16.

Next, a description of the present lock-up device 7 will be given. Inthe present lock-up device 7, the outer peripheral side torsion springs32 and the inner peripheral side torsion springs 33 operate until thestopper pins 46 come into contact with the end faces of the cutouts 35 bformed in the driven plate 35. Additionally, only the outer peripheralside torsion springs 32 operate after the stopper pins 46 have come intocontact with the end faces of the cutouts 35 b formed in the drivenplate 35.

The overall rigidity of the present lock-up device 7 is the same as theoverall rigidity in a case where the two outer peripheral side torsionsprings 32 of each set act in series because of the float member 42, soin the present lock-up device 7 also, as shown in FIG. 16, the normalmode (primary mode) of the lock-up device 7 can be maintained below thelock-up speed Na. Further, in the present lock-up device 7, the floatmember 42 is not involved in the vibration system of the lock-up device7, so even if the speed increases, the occurrence of resonance of thefloat member 42 can be suppressed (see the solid line in FIG. 16).Because of this, in the present lock-up device 7, as shown in FIG. 16,the vibration level can be kept below the allowable level.

Other Embodiments Different from Second Embodiment

(a) The present invention is not limited to the above embodiment and iscapable of various modifications and revisions without departing fromthe scope of the present invention. For example, in the aboveembodiment, the elastic members were configured by linear coil springs,but other elastic members can also be used. For example, instead oflinear coil springs, arc-shaped coil springs can also be used. In thiscase, torsion characteristics with various variations can be easilydesigned. Further, the numbers and lengths of the coil springsconfiguring the outer peripheral side and inner peripheral side torsionsprings are not limited to the above embodiment. Moreover, the floatmember 42 is for restricting the movement of the torsion springs(elastic members) toward the outer peripheral side, and the shape of thefloat member 42 is not limited to the above embodiment.

(b) In the above embodiment, an example of a case where the spring seats52 are attached to both end portions of each of the outer peripheralside torsion springs 32 was described. However, the shape and mode ofattachment of the spring seats 52 are not limited to the aboveembodiment and can be any shape and mode of attachment.

For example, as shown in FIG. 17, in the two outer peripheral sidetorsion springs 32 of each set, the one outer peripheral side torsionspring 32 a and the other outer peripheral side torsion spring 32 b canalso be coupled to each other by one spring seat 152. In this case, thetwo outer peripheral side torsion springs 32 can be attached betweenadjacent catch portions 31 a of the drive plate 31 in a state in whichthe two outer peripheral side torsion springs 32 have been integratedcoupled together by the spring seat 152. Because of this, in the case ofusing the spring seat 152 shown in FIG. 17, the efficiency with whichthe lock-up device is assembled can be improved compared to the case ofusing the separate spring seats 52 described in the above embodiment.

Further, as shown in FIG. 18, faces 252 a and 252 b of a spring seat 252that the two outer peripheral side torsion springs 32 a and 32 b contactcan be inclined. In this case, for example, the spring seat 252 isformed in such a way that the angle formed by the two faces 252 a and252 b formed on the spring seat 252 becomes a predetermined angle α. Byforming the spring seat 252 in this way, the compression direction ofthe two outer peripheral side torsion springs 32 a and 32 b of each setcan be appropriately guided in the axial direction of the outerperipheral side torsion springs 32. Because of this, it becomesdifficult for the two outer peripheral side torsion springs 32 a and 32b of each set to contact the float member 42, so the frictional forceacting between the outer peripheral side torsion springs 32 a and 32 band the float member 42 can be reduced. Because of this, the vibrationlevel of the lock-up device can be reduced.

(c) In the above embodiment, an example of a case where the spring seats52 are attached to both end portions of each of the outer peripheralside torsion springs 32 was described. However, provided that the twoouter peripheral side torsion springs 32 of each set can be caused toact in series, it is not invariably necessary to use the spring seats52. For example, the end portions of the two outer peripheral sidetorsion springs 32 of each set can also be brought into direct contactwith each other. More specifically, the end turn portions of the twoouter peripheral side torsion springs 32 of each set can also be broughtinto direct contact with each other. In this case, special members suchas spring seats become unnecessary, so the number of parts and the stepsrequired to install the spring seats can be reduced.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a lock-up device for a fluidcoupling for transmitting torque and absorbing and damping torsionalvibration.

1. A lock-up device for a fluid coupling for transmitting torque andabsorbing and damping torsional vibration, the lock-up device for thefluid coupling comprising: an input rotation member; an output rotationmember; a plurality of first elastic members that are compressed in arotational direction by relative rotation between the input rotationmember and the output rotation member; and a float member that is placedin such a way as to be rotatable relative to the input rotation memberin order to cause two of the first elastic members among the pluralityif first elastic members to act in series in a circumferentialdirection, the two first elastic members being are arranged adjacent toeach other in the circumferential direction, the two of the firstelastic members being configured at a predetermined distance away from acenter of the rotation the input rotation member, and a length of one ofthe two first elastic members in a free state being shorter than alength of the other of the two first elastic members, a rigidity of theone of the two first elastic members being greater than a rigidity ofthe other of the two first elastic members.
 2. The lock-up device forthe fluid coupling according to claim 1, further comprising a pluralityof second elastic members being configured on either one of an innerperipheral side and an outer peripheral side of the plurality of firstelastic members, the plurality of second elastic members beingconfigured to transmit the torque to the output rotation member, and amiddle member being configured in such a way as to be rotatable relativeto the input rotation member in order to transmit the torque from thefirst elastic members to the second elastic members.
 3. The lock-updevice for a fluid coupling according to claim 1, wherein the one of thetwo first elastic members is placed on a side to which the torque isinput by the input rotation member.
 4. The lock-up device for the fluidcoupling according to claim 1, wherein the other of the two firstelastic members is placed on a side to which the torque is input by theinput rotation member.
 5. The lock-up device for a fluid couplingaccording to claim 4, wherein a total length of the two first elasticmembers is predetermined.
 6. A lock-up device for a fluid coupling fortransmitting torque and absorbing and damping torsional vibration, thelock-up device for the fluid coupling comprising: an input rotationmember; an output rotation member; a plurality of sets of first elasticmembers that are compressed in a rotational direction by the relativerotation between the input rotation member and the output rotationmember; and a float member being configured to restrict movement of thefirst elastic members in a radial direction, the plurality of sets ofthe first elastic members being arranged adjacent to each other in acircumferential direction, the plurality of sets being configured atpredetermined distance away from a center of rotation of the inputrotation member, the plurality of sets being rotatable relative to thefloat member, one set of the sets including a plurality of springmembers, the plurality of spring members being arranged to be compressedin series continuously in the circumferential direction.
 7. The lock-updevice for the fluid coupling according to claim 6, wherein each of theplural spring members includes two ends, and the two ends are arrangedto be rotatable relative to the float member.
 8. The lock-up device forthe fluid coupling according to claim 6, wherein the torque istransmitted in the order of the input rotation member, the plurality ofsets of the first elastic members, and the output rotation member. 9.The lock-up device for the fluid coupling according to claim 6, whereinThe plurality of spring members are arranged in series continuously inthe circumferential direction via seat members.
 10. The lock-up devicefor the fluid coupling according to claim 6, wherein the plurality ofspring members are arranged in series directly and continuously in thecircumferential direction.
 11. The lock-up device for the fluid couplingaccording to claim 6, wherein the plurality of spring members are madeof linear coil springs or arc-shaped coil springs.
 12. The lock-updevice for the fluid coupling according to claim 6, further comprising aplurality of second elastic members being configured on either one of aninner peripheral side and an outer peripheral side of the plurality setsof the first elastic members, the plurality of second elastic membersbeing configured to transmit the torque to the output rotation member,and a middle member being configured in such a way as to be rotatablerelative to the input rotation member in order to transmit the torquefrom the first elastic members to the second elastic members.